Technical Details - Omron CQM1-ARM21 Operation Manual

Introduction
No termination

1-1-3 Technical Details

Concept
Communication principles
4
The network topology may be a star, a line with or without branch lines, or a
full tree structure. Termination is not required.
star
controller
Master
Slave
Slave
Slave
Slave Slave
Slave Slave
The maximum cable length for the total system may not exceed 100 m. By
using 2 repeaters and additional AS-Interface power supplies, this can be
extended to up to 300 m.
This section will provide some technical details of the AS-Interface system. It
is not essential to understand all details in order to operate the CQM1-
ARM21.
The aim of AS-Interface is to supply energy to, AND exchange I/O data with
slave stations over a simple unshielded two-wire cable. To achieve this, while
maintaining reliability and electromagnetic compatibility in an industrial
environment, a specific communication model has been developed which
ensures encoding without a DC signal component and a very narrow power
spectrum.
•
Messages are encoded in Manchester II format.
•
Modulation is by alternate pulse modulation (APM).
•
The transmitter, in both master and slave, acts as a current sink
generating sine-shaped pulses.
•
The characteristic impedance of the power supply unit transforms each
current pulse into a sin²-shaped voltage pulse.
• ) is defined as 6 µs, resulting in a bit sequence frequency
One bit time (T
Bit
of 166.67 kbit/s.
All communication on the AS-Interface line is controlled by the master. The
AS-Interface specification prescribes in detail which sequence of actions the
master must follow. On the highest level, the execution control is managed as
shown below:
branch lines
line
controller controller
Master Master
Slave
Slave
Slave
Section 1-1
tree
controller
Master
Slave Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave
Slave